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ECOSYSTEMS & MATERIAL CYCLES
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abiotic & biotic factors can change population size / change distribution
abiotic
Temperature: some plants can’t survive in cold temperatures
Amount of water: some roots unable to respire with too much water / some plants grow best with high moisture levels
Light intensity: grass in shade replaced by moss
Levels of pollutants: bioindicators
Biotic
Competition: species competing for same resource
Predation: Predator/prey cycle
Prey increase – lots of food for survival/reproduction of predator – predator increase
Prey decrease – more predators to eat them – Predator decrease – less/competition for food
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parasitism & mutualism
Mutualism: Relationship between two organisms where both benefit
Example: bird / crocodile – birds gets nutrients from cleaning crocodiles skin
Parasitism: Parasites live on/in host species – gets what it needs / leaves harm
Outside: nits
Inside: tape worm – suck nutrients from intestines, hooks & suckers to keep attached to intestines
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Determine number of organisms in given area
Quadrat: Number of organisms in total area = average x total area m2
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Efficiency = energy transferred to next level x 100
total energy supplied
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biodiversity conservation: effort to protect rare/endangered species
Areas of greater biodiversity recover faster from natural disasters
Preserve as many species as possible to form new varieties of plants and animals to provide what we need
Protect human food supply: conservation programmes prevent over-fishing – ensure fish for future generations
Minimal damage to food chains: 1 extinction impacts whole food chain
Providing future medicines: extinct plants containing undiscovered medicines – missing out
Cultural aspects: species may be part of Nation’s Cultural heritage – USA: Bald Eagle
Ecotourism & employment
Conservation schemes for At-Risk species
Animals: Protect species’ natural habitat / captive breeding programmes
Plants: seed banks – store/distribute seeds of rare/endangered plants
Reforestation: replanting variety of tree species over where forest previously was
Forest – high biodiversity: wide variety of plants – food/shelter for variety of animal species
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how different materials cycle through abiotic/biotic components of ecosystem
Abiotic components
Run-off of nitrates in farming (nitrogen compounds)
Fossil fuels
Lightning

Decomposer bacteria
Biotic components
Animals
Plants
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water cycle
Transpiration from plants / evaporation of sea from sun’s energy: water → water vapour
Warm water vapour rises – cools/condenses into clouds
Precipitation: clouds release water
Surface run-off: water back to sea
Potable water: water safe to drink
Desalination: removes salts
Salt water boiled in large enclosed vessel – water evaporates & separates from salt – condensed back to pure water
Reverse osmosis:
Salt water treated to remove solids
Fed at high pressure into vessel containing partially permeable membrane – only allows water
Pressure causes water molecules to move in opposite direction to osmosis: high → low salt concentration – separated
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Bioindicators: species’ presence/absence indicates condition/pollution level
Simple/cost-effective – don’t give accurate figures of how polluted area is
Non-living indicators: dissolved oxygen meters & chemical tests – measure concentration of dissolved oxygen in water
Electronic meters & various laboratory tests – measure sulphur dioxide concentration
Water pollution – eutrophication
polluted: bloodworm / sludge-worm
clean: freshwater shrimps / stonefly
Air pollution

Lichens: sensitive to sulphur dioxide concentration – fungus that grows on rock/trees (symbiosis between fungus/algae)
High concentration:
lichens can’t survive
crusty lichens
leafy lichens
Clean air:
lots of bushy lichens
Black spot fungus on roses: sensitive to sulphur dioxide concentration
Decomposition
Temperature: warm – speeds up rate of enzyme-controlled reactions – decay happens faster (too hot = enzymes denature)
Water content: decay faster when moist – organisms involved need water to survive & carry out biological processes
Oxygen availability: microorganisms need oxygen for aerobic respiration
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Compost (bins)
Temperature: some insulated / decomposers produce heat energy themselves
water content: moist
oxygen availability: mesh sides – increase availability
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